Thyroid nodules are extremely common — found in up to 67% of adults on ultrasound. The vast majority are benign. The challenge is identifying the small subset that requires biopsy. The ACR TI-RADS (Thyroid Imaging Reporting and Data System) 2017 provides a structured scoring system to guide this decision. Here's how to apply it in practice.

Normal Thyroid Measurements

Before evaluating nodules, know what normal looks like:

Parameter	Normal Value
Lobe length	4–6 cm
Lobe width	1.5–2.5 cm
Lobe AP	1.5–2.5 cm
Isthmus thickness (AP)	≤ 5 mm
Echogenicity	Homogeneously hyperechoic (brighter than adjacent muscles)

Thyroid volume = 0.524 × (length × width × height) for each lobe, summed.

Normal: 4–20 mL (women), 4–25 mL (men)

ACR TI-RADS Scoring System (2017)

The ACR TI-RADS assigns points in five categories. Total points determine the TI-RADS level and biopsy recommendation.

Category 1: Composition

Finding	Points
Cystic or almost completely cystic	0
Spongiform	0
Mixed cystic and solid	1
Solid or almost completely solid	2

Spongiform: Composed of tiny cystic spaces (> 50% of volume). Think "sponge." Strongly suggests benign colloid nodule.

Category 2: Echogenicity

Finding	Points
Anechoic	0
Hyperechoic or isoechoic	1
Hypoechoic	2
Very hypoechoic	3

Compare the nodule to adjacent strap muscles. "Very hypoechoic" = darker than the surrounding muscles. This is a significant finding associated with malignancy.

Category 3: Shape

Finding	Points
Wider than tall	0
Taller than wide	3

"Taller than wide" = the longest axis of the nodule is in the anteroposterior direction (perpendicular to the transducer surface). This is a strong predictor of malignancy (grows across tissue planes).

Measure in the transverse plane: Compare height (AP dimension) to width (transverse dimension). If height > width = taller than wide.

Category 4: Margin

Finding	Points
Smooth	0
Ill-defined	0
Lobulated or irregular	2
Extra-thyroidal extension	3

Lobulated: Small bumps along the margin. Irregular: Angular, spiculated, or not smooth. Extra-thyroidal extension: Nodule breaks through the thyroid capsule into adjacent structures. High suspicion for malignancy.

Ill-defined margins: Paradoxically, ill-defined (not sharply demarcated) margins score 0 — the concern is for clearly lobulated or irregular margins, not simply the inability to define the border.

Category 5: Echogenic Foci

Choose all that apply (add points for each):

Finding	Points
None or large comet-tail artifacts	0
Macrocalcifications	1
Peripheral (rim) calcifications	2
Punctate echogenic foci	3

Large comet-tail artifacts: V-shaped reverberation artifacts behind bright foci — represent colloid crystals. These are benign. Score 0.

Macrocalcifications: Large echogenic foci with clean posterior shadowing. Associated with both benign (dystrophic) and malignant (papillary thyroid cancer) processes.

Peripheral (rim) calcifications: Echogenic line along the nodule periphery. Eggshell or discontinuous rim calcification (especially with soft tissue extending through it) is more concerning.

Punctate echogenic foci: Tiny bright dots without comet-tail artifact. These represent microcalcifications — the pathological hallmark of papillary thyroid carcinoma. High specificity for malignancy. Score 3.

TI-RADS Levels and Recommendations

Total Points	TI-RADS Level	Biopsy Threshold
0	TR1 (Benign)	No biopsy
2	TR2 (Not suspicious)	No biopsy
3	TR3 (Mildly suspicious)	FNA if ≥ 2.5 cm; Follow if ≥ 1.5 cm
4–6	TR4 (Moderately suspicious)	FNA if ≥ 1.5 cm; Follow if ≥ 1.0 cm
≥ 7	TR5 (Highly suspicious)	FNA if ≥ 1.0 cm; Follow if ≥ 0.5 cm

FNA: Fine-needle aspiration biopsy Follow: Ultrasound surveillance without immediate biopsy

How to measure the nodule: Three perpendicular dimensions in two planes. Use the largest dimension for the size threshold decision.

Scanning Protocol for Thyroid Nodule Evaluation

Probe: 10–15 MHz linear transducer

Systematic scanning:

Isthmus: transverse and sagittal
Right lobe: transverse (apex to base) and sagittal; measure dimensions
Left lobe: same
Each nodule: describe and measure in transverse and sagittal

For each nodule, document:

Location: right lobe / left lobe / isthmus; upper/mid/lower pole
Size: three dimensions (length × width × height)
Composition
Echogenicity
Shape
Margin
Echogenic foci
Vascularity on color Doppler (peripheral vs central — not a TI-RADS criterion but worth noting)

Color Doppler: Document vascularity pattern. Primarily an adjunct finding — intense internal vascularity can be seen in malignancy but also in hypervascular benign nodules (toxic adenoma). Not included in TI-RADS scoring.

Lymph Node Evaluation

Always evaluate the cervical lymph nodes, particularly:

Level VI (central compartment — between the carotids)
Level III and IV (along the jugular chain)

Suspicious lymph node features:

Loss of fatty hilum
Round shape (short axis > 5 mm)
Cystic change within the node
Microcalcifications within the node
Peripheral vascularity

In the context of a suspicious thyroid nodule, abnormal cervical nodes raise concern for regional metastasis.

Common Mistakes in TI-RADS Scoring

Confusing comet-tail artifacts with microcalcifications: Comet-tail = V-shaped, behind the echogenic focus. Microcalcifications = punctate bright dots, no reverberation behind them. One scores 0, the other scores 3. This distinction matters enormously.

Not measuring in the correct plane for taller-than-wide: Shape must be assessed in the transverse plane. If you measure in sagittal, the shape assessment will be wrong.

Missing extra-thyroidal extension: Look carefully at the thyroid capsule around any suspicious nodule. Capsular irregularity or obvious extension beyond it adds 3 points and is clinically significant.

Counting each feature separately for echogenic foci: The scoring says "choose all that apply" for echogenic foci — if a nodule has both macrocalcifications and microcalcifications, score both (1 + 3 = 4 points from that category alone).

SonoBuddy's TI-RADS scoring guide and normal thyroid measurements are in the Measurements and Pathologies sections — search "thyroid" for quick reference.

Thyroid Nodules and ACR TI-RADS: A Practical Sonographer's Guide